Maximum pressure gauge



AEL, M, E45. K. J. DE JUHAsz 2,382,547

' MAXIMUM PRESSURE GAUGE Filed May 7.', 1941 8 ily f2 5 I5 /7a I 3a! 3 n um a@ NVENTOR Kal/MM f @RW Patented Aug. 14, 1945 UNITED STATES PATENT yOFFICE 2 Claims.

)ly invention relates to. improvements in gauges for measuring the maximum value of variable pressures, in particular that of cyclically recurring compression and combustion pressures occurring in cylinders of internal combustion engines, as exemplified by the United States Patents 1,904,747; 1,467,558; 1,950,532; 2,046,801 and l the piston just ceases which condition is indi` cated electrically by a piston-operated contactor actuating a signal-lamp preferably of the neonlamp type. The maximum pressure will be then indicated by the strain, l. e., the lengthening or shortening of the measuring spring which can be read on escale, micrometer, dial, or counter in terms of pressure units.

While this principle was found usable in practice yet it was found that these instruments are subject to errors due to the variability of the spring rate as a consequence of fatigue and temperature effects.

The object of my invention is to minimize these harmful influences and thus provide a pressure gauge of improved accuracy, and of greater con venience of operation.

The essential feature of myinvention is that the spring force transmitted to the piston is, in turn, produced by a fluid pressure which can be measured by a pressure gauge. In virtue of this feature the spring rate, as such, does not enter into the measurement and therefore its calibration, and its variability, have no effect on the accuracy of measurement. A second advantage is that the pressure gauge on which the pressure is read can be located at a distance from the engine cylinder to be tested. A third advantage is the facility by which my maximum pressure gauge lends itself to the measurement of pressures in a number of engine cylinders successively or even simultaneously. A fourth advantage is that not only the magnitude of the maximum pressure but also the engine phase at which lt occurs is capable of being indicated which is a valuable information for the equality or nonequality of load-distribution among the several cylinders oi' a multi-cylindered engine. l

,My linvention is illustrated by the attached drawing in which:

Fig. 1 shows the sectional elevation of the pressure-balancing unit and of the pump and pressure gauge unit, and the schematic arrangement of the neon-lamp circuit; V

Fig. 2 shows a modification of the neon-lamp arragement in which the neon-lamp is mounted on a disc which is rotated by the engine shaft;

Fig. 3 shows the view of the rotating neonlamp as it appears to the observer when the apparatus is being operated;

Fig. 4 shows the view of the rotating neonlamp when four pressure-balancing units actuate it simultaneously;

Fig. 5 shows the schematic arrangement cf the apparatus applied to a four-cylindered engine.

Fig. 6 shows the sectional elevation of a modiflcation of the pressure-balancing unit in which a bellows is used for transmitting the iiuid force to the compression spring;

Fig. 7 shows the sectional elevation of a modification of the pressure-balancing unit in which a tension spring is used to transmit the ud force to the piston;

Fig. 8 shows the sectional elevation of a modication of the pressure-balancingunit in which a diaphragm is used to transmit the fluid force to the piston. V

In the embodiment of the invention illustrated in Fig. 1 the barrel I is attached to the engine cylinder to be tested by means of the cone 2 and union nut 3. The piston 4 is a free but airtight fit in the barrel I, and is capable of an axial motion therein. On its under side the piston 4 is exposed to the variable pressure which is to be measured; onits upper surface it is acted upon by the force of the spring 5 which latter can be compressed to a greater or lesser extent by the hydraulic piston 6 movably arranged within the hydraulic cylinder 1. In order to produce the hydraulic pressure a hand-operated hydraulic pump is provided, consisting of -the ram I0, cylinder 9, threaded spindle II and hand-wheel I2. The space 9a, pipe 8 and space 1a are iilled with oil or other suitable liquid the pressure of which is measured by the pressure gauge I3. Thus the liquid pressure determines the compression of the spring 5 and produces a balancing pressure on the piston 4. The pressure gauge I3 is graduated preferably in units of this balancing pressure. It is to be noted that the pipe 8 can be of any convenient length making n possible the regulation and observation of the balancing pressure at any convenient location remote from the pressure-balancing unit and from the engine.

Depending on whether the balancing pressure is smaller or greater than the instantaneous value o! the variable pressure actins on the piston 4 the latter will tend to move upward or downward, i. e., in the direction of the lesser pressure. The range of motion of the piston 4 is limited to a small amount by means of the piston rim la which in the lowermost position of the piston lies on the upper surface of the barrel i, and in the uppermost position abuts against the lower extension of the hydraulic cylinder 1. The motion of the piston 4 actuates an electric contacter consisting of the lever I4, return-spring I5 and setscrew I6 in the manner shown, making or breaking the electric circuit consisting of the battery I1,

neon-lamp I8 and ground I9. The mass of the piston I, lever I4 and spring I5 are small, in virtue of which the making and breaking of the circuit takes place practically instantaneously, at the instant of the engine cycle at which the variable vengine pressure is equal to the balancing pressure as shown on the pressure gauge i3.

In operation, while the engine is running, the operator by turning the nandwheel i3 increases or decreases the balancing pressure until the flashes of the neon lamp I8 just disappear or just begin to appear. The pressure shown on the pressure gauge i8 will be then the maximum value of the variable engine pressure.

The phase o the engine cycle at which the maximum pressure occurs can be determined by mounting the neon lamp on a rotating disc dil, Fig. 2, keyed to, or positively driven by the engine shaft. In this oase the electric current has to be supplied to the neon lamp i8 through brushes ilo i905, and contact rings il?? and Illh. The observer will see a lighted segment, as shown in 3 by the hatched aree 22, sign-.dying the portion of the engine cycle, in terms o1 crank angle, during; which the balancing pressure is ei:- cedeci, and the duration of which can be read on the stationery protractor 2 i. Raising the balancing pressure the length of the lighted segment will decrease until it will naily disappear.

The application oi' my invention 'te fourcylinder engine is shown schematically on in which Btc, Eilat represent the four cylinders the engine, si the engine shaft, and 32a, 32h, elle, 37201 the four corresponding complete balancing pressure units mounted on each cylinder. A switch is provided by which the cena tactor pertaining to each engine cylinder can be made to actus-ite the neon lamp in turn. 0r, in certain cases it may he desirable to short the switch 33 with all the tour contact points simultaneously and thereby obtain on the rotating disc four lighted segments as shown by the hatched areas 22o, 22h, 22o, 22d on Fig. Il. In general, these lighted segments will not ce of equal length, nor located quite symmetrically around the protractor 2l, indicating thereby the fact that the pressure cycles of the several engine cylinders are not uniform. In possession of this information the operator can take suitable corrective measures onthe engine in order to bring about the desired uniformity and equality.

The foregoing description and illustrations serve to exemplify the invention. but various modlilcations of it are possible within the scope of the invention. For example, the pressure-balancing unit may be constructed with bellows ia as shown in Fig. 6 eliminating thereby the possibility of leakage, and reducing the friction. The spring l may be constructed as a spring working in tension` working in commotion with the hydraulic piston Ib as shown in Fig. 7, or, as a spring of other than helical type, such as a diaphragm lb working in commotion with the hydraulic piston lc as shown in Fig. 8. The neon lamp used as a visual indicator can be replaced by a telephone receiver wherever an audible indication is preferable. Instead of using one neon lamp for all the cylinders it is possible to use as many neon lamps as there are cylinders in the multi-cylindered engine. Other modifications of the elements and arrangement of my invention can be made by those skilled in the art without departing from the principle of my invention and from the scope of the appended claims.

What I claim is:

1. A pressure gauge for measuring the extreme value of a uctuating pressure comprising a body. a pressure-chamber arranged in said body, a pressure-responsive element arranged in Said presn sure-chamber exposed to said fluctuating pressure and exerting a pressure-force, c. spring under load exerting a spring-force on said pressureelement in opposition to said iluctuating reesure, a hydraulic loadinr,7 device exerting a regula ble load on said spring, a gauge indicating said regulable load, and signaling; mec-.ns actuated oy said pressure responsive element for indicating when the said iiuctuating pressure-force and regulable spring-force are in equilibrium.

2. A pressure gauge for measuring the extreme value of a periodically fluctuating pressure conlprising a. body, a pressure-chamber arranged in said body, a pressure-responsive element arranged in said pressure-chamber exposed to said fluctuating pressure and exerting a pressureforce, n spring under load exerting a spring-force on said pressure-element in opposition to said 'fluctuating pressure, a hydraulic loading device exerting a regulable load on said spring, a gauge indicating said regulable hydraulic load, an electric circuit including,r arnake and brealsdevice actuated by said pressure responsive element and an electric slgnaldamp for indicating when said iiuctuatine pressure-force and regulable springorce are in equilibrium, a cllsc rotatable in syrichronlsm with the period of fluctuation of the pressure to be measured, said signal-lamp being mounted on said disc, a protractor for showing the phases of `the periodical pressureeluotuation in which the uctuatlng pressure-force and the regulable spring-force are in equilibrium.

KALMAN JOHN DE JUHASZ. 

